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Isaac Newton Institute for Mathematical Sciences

Special Week on Quantum Cryptography

A Generic Security Proof for Quantum Key Distribution

6th September 2004

Authors: Matthias Christandl (University of Cambridge), Renato Renner (ETH Zurich), Artur Ekert (University of Cambridge and National University of Singapore)


Quantum key distribution allows two parties, traditionally known as Alice and Bob, to establish a secure random cryptographic key if, firstly, they have access to a quantum communication channel, and secondly, they can exchange classical public messages which can be monitored but not altered by an eavesdropper, Eve. Quantum key distribution provides perfect security because, unlike its classical counterpart, it relies on the laws of physics rather than on ensuring that successful eavesdropping would require excessive computational effort. However, security proofs of quantum key distribution are not trivial and are usually restricted in their applicability to specific protocols. In contrast, we present a general and conceptually simple proof which can be applied to a number of different protocols. It relies on the fact that a cryptographic procedure called privacy amplification is equally secure when an adversary's memory for data storage is quantum rather than classical.